Tagging songs downloaded from Mix Radio

Hi, I have a problem with Mix Radio songs. When I use a music player which has offline indexing, it always reads them without the tag. I tried importing my library to a PC and use Picard, but that couldn't edit the tags of these songs. A lot of the songs I have are not that easily available on websites to download and I don't want to cross my FUP limit. Can someone please give a solution to this, I only listen songs to songs on my laptop and this is bad
Thank you!